Diatoms of North AmericaPaleolimnology is the study of lake sediments. Why study lake sediments? Lake sediments contain the history of a lake. When diatoms, soft algae, zooplankton, pollen and other organisms in a lake die, they settle to the bottom. The organisms accumulate over time, forming layers that represent past years, to decades, to hundreds and thousands of years.
This summer, students worked together to obtain a sediment core from the depths of West Lake Okoboji. The core represents approximately a few hundred years of history; it goes back to the early days of agriculture in Iowa. After the students retrieved the core, they traveled to the National Lacustrine Core Facility (LacCore) in Minneapolis. There, the core was imaged and split into two sections, with one section archived at LacCore.
During the course, students learned to interpret the presence of diatom species in relation to the history of past events. For example, in West Lake Okoboji, increases in Cavinula scutelloides followed changes in agricultural practices, resulting in a decline in water quality. In another lake (Widow Lake, Lassen Volcanic National Park, California), biraphid diatoms increased in the lake following volcanic eruptions that deposited tephra in the lake. Students examined diatoms within the cores, focusing on the biology and ecology of Cavinula scutelloides, Hippodonta capitata, and Staurosira construens var. binodis. Students then added their observations and data to iNaturalist, bringing the total count to 703 posts over the years of the summer course.
To share their knowledge of diatoms with the public, students hosted local kids at Iowa Lakeside Lab. Kids learned that although diatoms have fancy Latin names, they happen to be shaped shaped like boats, cheese wedges, mustaches, and pizza!
Future investigators may visit LacCore to request the "Hard-Core Core" :)
